1. Field of the Invention
The present invention relates to a three-dimensional drawing model generation method and three-dimensional drawing method suitable for computer graphics (CG) and computer aided design (CAD), and a program thereof, and more particularly to a three-dimensional drawing model generation method and a three-dimensional model drawing method for decreasing the number of polygons using texture mapping, and a program thereof.
2. Description of the Related Art
Systems for constructing three-dimensional virtual models, such as mechanical products and electric components, on a computer are widely used in the field of computer graphics and computer aided design.
To express three-dimensional models, a model surface is defined by small polygons, by which various shapes are expressed. As FIG. 34 shows, if a three-dimensional object 1000, which has many holes 1020 on one face 1010, is modeled with polygons, the face 1010 is expressed by many triangular polygons so as to express the holes 1020. In other words, the face 1010 is defined as data using a large volume of polygon data (three-dimensional vertex coordinates).
If this three-dimensional model is large scale or complicated, the number of polygons increases, so the drawing processing amount increases, which makes it difficult to draw at high-speed. Although the drawing processing capability is improving due to advancements in hardware, three-dimensional models are also becoming more complicated and are increasing in scale, so it is difficult to draw large scale models, such as automobiles, airplanes, ships and factory lines, smoothly.
When an entire view of a large model is drawn, small convex and bump portions are drawn small, and are hardly seen. Therefore, by making the area with such small bumps to be texture, small polygons can be decreased.
As FIG. 35 shows, texture is a drawing technology for mapping the texture images 1030-1 and 1030-2 on the face 1010 comprised of several polygons 1010-1 and 1010-2, and fine patterns can be drawn at high-speed. A model to express this texture is called a texture model.
In a three-dimensional object (three-dimensional model), it has been proposed to automatically create texture on the face defined as a plane by a two-dimensional graphic function, as shown in FIG. 35 (e.g. Japanese Patent Application Laid-Open No. 2002-063222).
According to this conventional method, the number of polygons can be decreased by a texture model, but even with this, many planes exist in a three-dimensional model with complicated shapes, and the number of polygons thereof is enormous. Therefore further improvement is necessary to draw a three-dimensional model with complicated shapes smoothly.